Plant Anatomy 2006-2007

Basic plant anatomy 3 root shoot (stem) leaves root tip root hairs nodes internodes buds terminal or apical buds axillary buds flower buds & flowers leaves mesophyll tissue veins (vascular bundles)

Leaves Function of leaves simple vs. compound photosynthesis energy transformation organic matter production gas exchange transpiration simple vs. compound

colored leaves (poinsetta) Modified leaves tendrils (peas) spines (cacti) succulent leaves colored leaves (poinsetta)

Interdependent systems Both systems depend on the other roots depend on sugars produced by photosynthetic leaves shoots depend on water & minerals absorbed from the soil by roots sugars water & minerals

Plant TISSUES Dermal Ground Vascular epidermis (“skin” of plant) single layer of tightly packed cells that covers & protects plant Ground bulk of plant tissue photosynthetic mesophyll, storage Vascular transport system in shoots & roots xylem & phloem

Parenchyma Parenchyma cells are unspecialized, thin, flexible & carry out many metabolic functions all other cell types in plants develop from parenchyma

Collenchyma Collenchyma cells have thicker primary walls & provide support help support without restraining growth remain alive in maturity the strings in celery stalks are collenchyma

Sclerenchyma Thick, rigid cell wall Cells for support lignin (wood) cannot elongate mostly dead at maturity Cells for support xylem vessels xylem tracheids fibers rope fibers sclereids nutshells seed coats grittiness in pears

Structure–Function again! Vascular tissue vessel elements Xylem move water & minerals up from roots dead cells at functional maturity only cell walls remain need empty pipes to efficiently move H2O transpirational pull vessel element dead cells Aaaah… Structure–Function again! tracheids

Phloem: food-conducting cells carry sugars & nutrients throughout plant sieve tube companion cell sieve plate plasmodesmata living cells

Phloem: food-conducting cells sieve tube elements & companion cells

Structure–Function again! Aaaah… Structure–Function again! Phloem Living cells at functional maturity cell membrane, cytoplasm control of diffusion lose their nucleus, ribosomes & vacuole more room for specialized transport of liquid food (sucrose) Cells sieve tubes sieve plates — end walls — have pores to facilitate flow of fluid between cells companion cells nucleated cells connected to the sieve-tube help sieve tubes